Sometimes when I'm stuck for ideas, I take a common/boring idea, then I add a twist. We walked through a store once and I told my daughters to look at every object in the store and add the phrase "...but with candy" to the end. In no time we had several good ideas, several ridiculous ideas, and several funny ideas.
Another way is to combine two seemingly unrelated ideas.
Then there are the "What if...?" scenarios. Talk it out with someone else if you can, they might have one half of an idea, and you can supply the other half.
